Sent from my iPad > On Jan 8, 2019, at 2:33 PM, Tomasz Figa <tfiga@xxxxxxxxxxxx> wrote: > >> On Mon, Jan 7, 2019 at 2:30 AM Ayaka <ayaka@xxxxxxxxxxx> wrote: >> >> Hello Ezequiel >> >> Sent from my iPad >> >>>> On Jan 7, 2019, at 1:21 AM, Ezequiel Garcia <ezequiel@xxxxxxxxxxxxxxxxxxxx> wrote: >>>> >>>> On Sun, 6 Jan 2019 at 13:16, Ayaka <ayaka@xxxxxxxxxxx> wrote: >>>> >>>> >>>> >>>> Sent from my iPad >>>> >>>>> On Jan 7, 2019, at 12:04 AM, Ezequiel Garcia <ezequiel@xxxxxxxxxxxxx> wrote: >>>>> >>>>> On Sun, 2019-01-06 at 23:05 +0800, Ayaka wrote: >>>>>>> On Jan 6, 2019, at 10:22 PM, Ezequiel Garcia <ezequiel@xxxxxxxxxxxxx> wrote: >>>>>>> >>>>>>> Hi Randy, >>>>>>> >>>>>>> Thanks a lot for this patches. They are really useful >>>>>>> to provide more insight into the VPU hardware. >>>>>>> >>>>>>> This change will make the vpu encoder and vpu decoder >>>>>>> completely independent, can they really work in parallel? >>>>>> As I said it depends on the platform, but with this patch, the user space would think they can work at the same time. >>>>> >>>>> >>>>> I think there is some confusion. >>>>> >>>>> The devicetree is one thing: it is a hardware representation, >>>>> a way to describe the hardware, for the kernel/bootloader to >>>>> parse. >>>>> >>>>> The userspace view will depend on the driver implementation. >>>>> >>>>> The current devicetree and driver (without your patches), >>>>> model the VPU as a single piece of hardware, exposing a decoder >>>>> and an encoder. >>>>> >>>>> The V4L driver will then create two video devices, i.e. /dev/videoX >>>>> and /dev/videoY. So userspace sees an independent view of the >>>>> devices. >>>>> >>>> I knew that, the problem is that the driver should not always create a decoder and encoder pair, they may not exist at some platforms, even some platforms doesn’t have a encoder. You may have a look on the rk3328 I post on the first email as example. >>> >>> That is correct. But that still doesn't tackle my question: is the >>> hardware able to run a decoding and an encoding job in parallel? >>> >> For rk3328, yes, you see I didn’t draw them in the same box. >>> If not, then it's wrong to describe them as independent entities. >>> >>>>> However, they are internally connected, and thus we can >>>>> easily avoid two jobs running in parallel. >>>>> >>>> That is what the mpp service did in my patches, handing the relationship between each devices. And it is not a easy work, maybe a 4k decoder would be blocked by another high frame rate encoding work or another decoder session. The vendor kernel have more worry about this, but not in this version. >>> >>> Right. That is one way to design it. Another way is having a single >>> devicetree node for the VPU encoder/decoder "complex". >> No, you can’t assume which one is in the combo group, it can be various. you see, in the rk3328, the vdpu is paired with an avs+ decoder. That is why I use a virtual device standing for scheduler. > > First of all, thanks for all the input. Having more understanding of > the hardware and shortcomings of the current V4L2 APIs is really > important to let us further evolve the API and make sure that it works > for further use cases. I replied the problems of the v4l2 request API in the other threads. I am waiting the feedback from those threads. > > As for the Device Tree itself, it doesn't always describe the hardware > in 100%. Also please note the merged device tree for the video codec won’t fix for most of the rockchip platform. > Most of the time it's just the necessary information to > choose and instantiate the right drivers and bind to the right > hardware resources. The information on which hardware instances on the > SoC can work independently can of course be described in DT (e.g. by > sub-nodes of a video-codec complex OR a set of phandles, e.g. > rockchip,shared-instances), but it's also perfectly fine to defer this > kind of knowledge to the drivers themselves. I wish there is a common mechanism for those device would share some resources. Although there is a multiple functions framework, but that is not I want. They are multiple functions but they are used at the same time not separately. > > Best regards, > Tomasz
